Re: [Visualpython-users] Beta test version of VPython for Python 3.1 for Windows

Here's another successful test. I replaced the import statements at
the start of the example program gas.py with the following import
statements, and deleted the old Numeric code in a try structure:

from visual.cvisual import (vector, mag, mag2, norm, dot, cross, rotate,
                       comp, proj, diff_angle, rate, waitclose)
from visual.primitives import (arrow, cylinder, cone, sphere, box, ring, label,
                               frame, pyramid, ellipsoid, curve,
faces, convex, helix,
                               points, text, distant_light, local_light)
from visual.ui import display
import visual.crayola as color
import visual.materials as materials
import visual.site_settings
import atexit as _atexit
_atexit.register(waitclose)
from math import pi, sin, cos, exp
from numpy import (sqrt, array, newaxis, add, less_equal, identity,
                   sort, nonzero, greater_equal, arange)
from visual.graph import (gdisplay, gcurve, ghistogram)
from random import random

This could have been more selective, since gas.py uses only a few of
the vector and primitive features. Also, gas.py already has a scene =
display(....) statement.

A subtle point that one should be aware of: In visual's __init__.py
there is some complex machinery to deal with the fact that when, for
example, you're taking the square root of a scalar you want to use the
math module's sqrt, because it is much faster than using numpy's sqrt.
On the other hand, you need to use numpy's sqrt if you're taking the
square roots of all the elements of a numpy array. For functions such
as sqrt you would want to do something like this:

from math import sqrt as msqrt
from numpy import sqrt as nsqrt

Then you would use msqrt or nsqrt depending on the argument. The
machinery in __init__.py takes care of this for you and applies the
faster sqrt when the argument is a scalar.

Bruce Sherwood